bytecode

问题 Some time ago, I asked in Embed the existing code of a method in a try-finally block how to wrap the body of a method in a try-finally block using ASM. The solution was to visit a label for the try block at the beginning of the method body in visitCode() and to complete the try-finally block when visiting an instruction with a return opcode in visitInsn() . I was aware that the solution won't be working if a method has no return instruction which applies if the method is always leaving with

问题 By "Magic" I mean the methods which have semantics which are not expressed in pure Java. I know all native methods are magic, in that their implementation is provided by the underlying runtime and not by Java bytecodes. Is the reverse true? Are all magic methods native , or are there some magic methods apparently implemented in pure Java, but with some extra help from some JVM-special-casing? The use case is that I want to modify the semantics of Java by instrumenting its bytecodes. All these

问题 I am writing a Bytecode instrumenter. Right now, I am trying to find out how to do that in the presence of objects. I would like some clarifications on two lines I read in the JVMS (section 4.9.4): 1) "The verifier rejects code that uses the new object before it has been initialized." My question is, what does "uses" mean here? I'm guessing that it means: passing it as a method attribute, calling GETFIELD and PUTFIELD on it, or calling any instance method on it. Are their other forbidden uses

问题 I was reading about instruction set in wiki and I came across this paragraph: Some virtual machines that support bytecode as their ISA such as Smalltalk, the Java virtual machine, and Microsoft's Common Language Runtime, implement this by translatin the bytecode for commonly used code paths into native machine code. In addition, these virtual machines execute less frequently used code paths by interpretation (see: Just-in-time compilation). Transmeta implemented the x86 instruction set atop

问题 Does class file format provide support for final keyword in case of using it with variables? Or does it just deduce the effective finality of a variable from code and JIT compiler perform optimization based on it? Here, in class file format documentation, they mentioned about final keyword, but only in case of using it with final block and final class . There is nothing about final variables . 回答1: No, there is no such information encoded in class file. You may easily verify this by compiling

问题 I am doing it for learning purpose. I have gone through many articles that php first convert its source code to bytecode, but i am not able to find a way to see the bytecode format, that how it looks like? In java and C there are many ways to see bytecode file. but unable to find any article in php to see converted bytecode. 回答1: To turn PHP code into a list of opcodes, you can use vld, the "Vulcan Logic Dumper" (available on GitHub and PECL). The PHP documentation also maintains a list of

问题 Say I do: #!/usr/bin/env python # encoding: utf-8 class A(object): pass Now I disassemble it: python -m dis test0.py 4 0 LOAD_CONST 0 ('A') 3 LOAD_NAME 0 (object) 6 BUILD_TUPLE 1 9 LOAD_CONST 1 (<code object A at 0x1004ebb30, file "test0.py", line 4>) 12 MAKE_FUNCTION 0 15 CALL_FUNCTION 0 18 BUILD_CLASS 19 STORE_NAME 1 (A) 22 LOAD_CONST 2 (None) 25 RETURN_VALUE Now I add some statements in the class definition: #!/usr/bin/env python # encoding: utf-8 class A(object): print 'hello' 1+1 pass

问题 I have a method of a class in a jar whose body I want to exchange with my own. In this case I just want to have the method print out "GOT IT" to the console and return true; I am using the system loader to load the classes of the jar. I am using reflection to make the system classloader be able to load classes by bytecode. This part seems to be working correctly. I am following the method replacement example found here: asm.ow2.org/current/asm-transformations.pdf. My code is as follows:

问题 I made a simple class to learn how to read Java byte code. What does the line Stack=1, Locals=1, Args_size=1 mean in the folloiwng code? public Demo(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return LineNumberTable: line 1: 0 回答1: It means you have one argument (the object to be initialised), one local variable (the object to be initialised) and at most one object on the stack (the object to be intialised) 来源： https:/

问题 In Python, I'd like to write a function that would pretty-print its results to the console if called by itself (mostly for use interactively or for debugging). For the purpose of this question, let's say it checks the status of something. If I call just check_status() I would like to see something like: Pretty printer status check 0.02v NOTE: This is so totally not written for giant robots ================================= System operational: ... ok Time to ion canon charge is 9m 21s Booster